Stabilizing means for vehicle steering axles



Sept 4, 1956 A. c. STOVER 2,761,693

STABILIZING MEANS FOR VEHICLE STEERING AXLES Filed Dec. 22. .1952 3 Sheets-Sheet 1 Q if ' INVENTOR. (u 400/ C. Jraveh- I E BY J A7'7'0ANf Sept. 4, 1956 A. c. STOVER 2,761,693

STABILIZING MEANS FOR VEHICLE STEERING AXLES Filed Dec. 22. 1952 5 Sheets-Sheet 3 INVENTOR. l-l 24/2627 C Jim er" "travel; as the first axle. y

It has been proposed tostabilize the action of {the turnv V H. "H U .u. a, .....".o r 5- Ancil swim, Louisville, Ky.; vassignor to William I i l srenhau Wil a P- E wood, "Id E senhauet and e h E- s h ue c n ines d bu i s under the name of The Eisenha'lier M1 pointing cdm annvan Wert,. i0 1 Application December 22, 195 2, Serial No'. 3275231 '14 Glaims. v or. zany-T31 This invention relates to hydraulic stabilizing means fo'r' vuse in connect-ion with vehicles having spaced: pairs of ground engaging steering wheels;

The present invention finds particular use in connectionwith vehicles of the type having tandemly arranged axles supported for turning movement about sublstantially vertically extending axes. it is desirable to stabilize the action of the axles so that turning movement of one axle in one direction insures a turning movement of a second axle in the opposite direction throughout approximately the same angle .of

ing axlesby connecting the axles with a closed hydraulic system comprising a pair of double acting'hydrauliccylindersan'cl fluid linesor conduits respectively connecting the cylinders at opposite sides of the pistons therein. The

pistons arerespectively mechanically connected to the axles in a man e u ha a in h u a uli dztcflm steering axle tending to turn the latter about a ventical axisisimparted to another turning axle tending to turn the latter axle about asecond vertical axis in a direction opposite the first axle. Thus turns of relatively sh radii may e ea i y ne t d ardlessq th the vehicle, and at'thesarne same the action of theirunning gear of the vehicle under severe road condi stabilized.

The cifectivenessof thehydraulic displacen entt system I I to stabilizethe action of the runninggearunder all i tic r epend a g y on h the q n h t be -ltept;,fre e-ofair throughout continued use. m ai ,ent intfhehydraulicsysternwouldbecornpiesse y recs transmit e y th un e a n W ee s 2611 El i-fie and hence would destroy the positive control ne c'essat' y fo al c ssf zo e a sn th vs sl v the above in view-it an object of this ,inv

to -prov d me n -f u t all airt Qmth x 5; i s s e an thsr b ur Po t v 9 turngaxlesofythevehicle. More part u 'm ea ion con em l =r9n i l zf X tem t xxes q throu th ms ltmi 9 a ..e fitat a valves. The aspiratingtvalvesare respectivelyc ne cted in opposite sides of the system and are 9p;er t d y d; plaeernent'of fluidin the system to expel a r from the latter,into the reservoir.

The foregoing. as .well as other ohj ect's win 15s mane rnor'e apparent as this description proceeds sp hen i im idst x o n ct- 0 w th th lac' 'qmpaay gs ##W- TQ S'WhQF A Figure l isa diagranirnatic plan View. of-a vehicle having tandemly arrangedjsteering'axles and p e stabilizing-means embodying the featilres of tlns nveiiim i a .s wt iv aqna v q z r fltt flab. wins me ns;

Figure 4 is an ennrges'wngiiudifiai seminar view In vehicles of the above type 3 Patented Sept. 4, 1956 l H PSZ 9 9 th r S at a sp h n. Figlir E gure s a cross sectional view taken on the line fFigure 4; and

x 1 is a cross sectional view taken on the line tiwfie fiiss e, a r

v P t th 91 .159 f il us a on h r entipventicais haw n .w s s w th a h c e o e en r t pe shawl}? my s w sin app ic on Se Q- 119 2 fil d Q ctober g novv Patent 2,6 43 ,895. Such avehicle 'll ateddiagra rnmatically in Figure l and comprises n a p g i isfif b 10 a as' mns e ght sernbly lun'sprung Weightassernbly 10 has tandemly arranged axles and l ispaced from one anothler longitudinally of the vehicle. Ground engaging wheels 15 a? a wa d mo e en s i t ax e and suspe ion :Tsp'rin'gs '(not shown) are provided tor 'ectii i'g axlesto the sprung weigh t 11.

he 13 is connected to operating .rnernber l6 ten 24 is c nn'ected to the operating member Ifi'hy a rod 351 ename as t u in i mo t the ';1 PPS t d ii t s about he" axis. 17 ause g movement of the piston 24 inopposite directiqns in 6 other, T W 26 rojects fth usli th endof cylinder and asuitable packing is pro- ,p s es th ssqape o v flsisf tsmth t ia s Zl- PZ i posi q edja .lh j i S d? .Q fll ar se g st-an 271 'Q'f ys m hu r de r be l wil be r p itqm a fth idew n ha t m a ate- Y'w' ed a out??? e i lr sas 1 a d '9 'h" a ne 'at d e r n P es e se aa pn "E Q l i 1i T js ef s me he'ih esuit" of tlie" normal steering of the vehicle" around curves forces or they may result from any one of a number of different conditions that may be encountered during operation of the vehicle. The construction is such that under normal operating conditions where the inherent steering action, or the degree of directional stability is equal for each axle, little or no force is transmitted from one axle to the other through the hydraulic system 20. However, should the wheels on one or the other of said steering axles encounter unequal turning thrusts, the construction is such that a force applied to one axle tending to turn the latter in one direction about its vertical mis is transmitted through the displacement system 26 to the other axle tending to impart a turning movement to the latter axle in the opposite direction. Thus, the turning thrusts which are not the function of normal steering of the vehicle are balanced or nearly so-by the hydraulic system 29 and directional stability is assured.

The foregoing action is required in order to exercise positive control of the steering axles and is accomplished providing the hydraulic system 7.0 is free of air. Should there be any appreciable amount of air present in the hydraulic system synchronous movement of the turning axles would be destroyed due to the fact that the air would be compressed and thereby affect the displacement required to obtain positive control of the steering axles.

In order to assure excluding air from the system 20 both sides 30 and 31 are respectively connected to the reservoir 42 by a pair of aspirating valves 43 and 44. As shown in Figure 4 of the drawings, the aspirating valve 43 has a body 45 formed of two parts 46 and 47. A receiving chamber 48 is formed in the bottom part 46 and diametrically opposed ports 49 and 50 extend through the side walls of the part 46. The port 49 is connected to one branch 30 of the fluid conduit 30 forming one side of the hydraulic displacement system 20 and the port 50 is connected to the other branch 30" of the fluid conduit 30. The lower end of the chamber is open and is normally closed by a removable cap 51 secured to the bottom of the part 46 by studs 52. A gasket 53' is interposed between the cap 51 and the bottom of the part 46 to prevent the escape of fluid from the chamber 48.

Inasmuch as the system 20 is completely filled with fluid, it follows that the chamber 48 is also filled with fluid and that displacement of fluid in the conduit or side 30 of the system 20 results in a movement of fluid through the chamber 48. Due to the velocity of flow of fluid through the conduit 30 during displacement, any air present in this side of the system tends to accumulate within the chamber 48 above the ports 49 and 50. This action is facilitated by providing the cap 51 with a baflie 53 which extends upwardly from the cap 51 into the chamber 48. As shown in Figure 4 of the drawings the baffle 53 is centrally located in the chamber 43 midway between the ports 49 and 50 in a position such that fluid entering the chamber 48 through either of said ports is deflected by the baffle 53. The resulting opposition to flow of fluid directly from one port to the other assists air in the side 30 of the system to pass upwardly in the chamber 48 and become trapped at the top of the latter chamber.

Referring again to Figure 4 of the drawings it will be noted that the top of the part 46 is reduced and is externally threaded to threadably engage the lower end of the body part 47. An O-ring type seal 54 is provided between the reduced portion of the part 46 and the adjacent inner surface of the part 47 to establish a fluid tight seal therebetween. The reduced portion of the part 46 has a vertically extending passage 55 centrally disposed with respect to the chamber 48 and reduced in diameter at the lower end to form an annular seat 56 intermediate the ends thereof. The upper end of the passage 55 opens into the bottom of a vertically extending circular transfer chamber 57 formed in the body part 47 and communicating with the interior of the reservoir 42. In detail the upper end of the body part 47 is threaded into a coupling 58 which is located within an opening formed in the bottom wall 59 of the reservoir 42 and is welded or otherwise secured to the wall 59. A vertically extending passage 60 is formed in the upper end of the body part 47 and connects the transfer chamber 57 to the interior of the reservoir. The passage 60 is aligned with the passage and is enlarged at the lower end to provide an annular seat 61 intermediate the ends thereof.

Supported within the chamber 57 for vertical sliding movement is a plunger 62 having an enlargement 63 intermediate the ends polygonally shaped in cross section, as shown in Figure 5 of the drawings. The corners of the enlargement 63 are rounded to have a bearing engagement with the inner surface of the chamber 57 and the faces of the enlargement between the corners cooperate with the inner surface of the chamber 57 to form vertical passages for fluid. The lower end 64 of the plunger 62 is shaped to have a sliding fit in the upper enlarged end of the vertical passage 55, and terminates in a conical end surface 65 adapted to engage the seat 56 in the normal or lowermost position of the valve plunger 62. An O-ring type seal 66 is supported Within an annular groove formed in the inner surface of the passage 55 in a position to establish a fluid tight seal with the end 64 of the valve plunger 62 in its normal or lowermost position.

The upper portion 67 of the valve plunger 62 is shaped to have a sliding fit in the enlarged lower end of the vertical passage and the upper end of the portion 67 is engageable with the annular seat 61 in the passage 60 to limit the extent of upward displacement of the plunger 62. An O-ring type seal 68 is supported within an annular groove 69 formed in the enlarged lower end of the passage 60 in a position to engage the upper end portion 67 of the valve plunger to establish a fluid tight seal.

The valve plunger 62 is in its normal position shown in Figure 4 when there is no displacement of fluid in the side 30 of the system 20. In this normal position of the valve plunger 62, the lower end 64 projects into the passage 55 and the conical end of the plunger engages the seat 56 to close communication between the receiving chamber 48 and the transfer chamber 57. Also in this normal position of the valve plunger 62, the upper portion 67 is spaced below the passage 60 to establish communication between the transfer chamber 57 and the interior of the reservoir 42.

When the valve plunger 62 is in the above mentioned normal position and fluid is displaced within the conduit or side 30 of the system 20 for any reason, an upward thrust is exerted on the valve plunger sufiicient to raise the latter to its uppermost position. As the valve plunger 62 moves to its uppermost position, the lower end 64 leaves the enlarged upper end of the passage 55 and the top portion 67 of the plunger projects into the enlarged lower end of the passage 60. Hence, the chamber 48 is open to communication to the transfer chamber 57 and communication between the latter and reservoir 42 is closed. Any air trapped in the chamber 48 passes upwardly through the passage 55 into the chamber 57 and is replaced by oil or non-compressible fluid previously admitted to the chamber 57 in the normal position of the valve plunger 62.

When the hydraulic system 20 returns to a condition of equilibrium the valve plunger 62 returns to its normal or lowermost position allowing any air previously admitted to the chamber 57 to pass upwardly into the reservoir. It follows from the above that the aspirating valve 43 functions each time fluid is displaced in the conduit or side 30 of the system 20 to expel any air that may be present in the side 30 of the system 20.

The valve plunger 62 is of such construction that in intermediate positions, the opposite ends of the plunger respectively remain in the passages 55 and 60 so that at no point in the stroke of the plunger 62 is it possible for hydraulic fluid to bypass the plunger. Thus, the volume of hydraulic fluid required to operate the plunger 62 cannot exceed the displacement of the valve plunger and this t i r't asea atis vq yst al i aq ari s o d s ement-of the pistons'in the system 2'0; "Gons'eqiientlwvery little movement of the pistons is required to actu'atetlie valvep lungerfizi M i flhe asp'irating valve 44 is identical in construction to the valye l-ia aridhence the same reference numerals are used "to indicate corresponding parts of the two yalves. "Itis to be noted, however, that the aspiratingyalve 44 connects the branches 31 and 31 of thefconduit 31 forming the opposite side of the system 'lll. 'Thopieration of the aspirating valve 44 to expel air from the side 31' of the system upon displacerneii't of hydraulic 'fiuid in thela-tter' side ofthe system "isth e same a's the operation of the valve 4;.3 previously described. Referring now'rnore in' detail ftothe reservoir 42 it will "be noted that the top wnme is fashioned with an open- -ing -7-l through which hydraulic fluid may be introduced into-the reservoir. A sleeve 721s welded or otherwise suitably secured to the top wall=70 in alignment'with the opening -71 and is interrially threaded to threa'dably engage a cap 46. The cap 7-3 coacts" With-the upper end' of the sleeve {7-2 to seal the interior ofthe reservoir from the atmosphere. The numeral 74 designates a suitable dip stick secured in any suitable'm anher at the upper end tothe cap 73 and adapted to indicate 'thelevel of thehydraulic fluid Within the reservoir he'hydraulic'fluid contained inthe reservoir 42 is main- -tained under pressure somewhat above atmospheric and inorder to accomplish this result air under pressure is introduced into the reservoir 42 through an opening iii-the top wall 7 t Asshown in Figure Q of the drawings, asleeve 76 is Welded or otherwise suitably secured to -'the top wall ll) 'in -alignment'with the openin-g 75 and isinternally threaded atthe upper. end to receive a nipple 77.

A pipe -T' 78is secured to the nipple and 'ofi outlet of the pipe T 78 is connected to an'airinlet valve 79 through the medium of -a -nipple 80 Theother outlet of thepipe T 78 is connected to an-air supply'line 'SZ through a'pressure regulatingvalve 81 which is set to maintain the pressure Within the reservoir 42 within the desiredlimits. Referring again-to Figure 2 0;? the-drawings -a shut-off valve -'83 'is shown in the air supply-line -t 6 enable closing t-he=latt er when-desired.

It is-preferred-to maintain the hydraulic fluidin the reservoir 42 underpressure above 'Jatmospheric in order .to render the aspir'atingvalves 43 and 44 more responsive to displacement of hydraulic-fluid in the system-20. Also by pressurizing the system the pressurein the i-latteri's prevented from dropping below atmospheric pressure. and hen ce the seals around the-piston rods will not be-subjected-to reversal of pressure. -Thus, the tendency {for ainto leak into the-systemyalongthe-piston ro'dsf'is 1 edu ced-- to --a minirnum and satisfactory operation is ob- I gained. even though the -seals may become worn.

Referring again to *Figu'res Z-and -3 of the drawings,

iit will be noted that provision. is made for bypassing. the iaspirating valves during refilling ofthe-reservoir 14 2.' In

detail the receiving chamber 48 0feach aspirating -valve is cOnnectedto the lower end ofabypasslline 84 by means of the coupling 85 and the upper end'of each bypassline "SA-is connected to the reservoir by affitting 56. -E achffitting86 is provided with a shut-ofi valve -87 andpthis valve is closed during the normal operation of thastab lizinam easili wev when iti d' s fi w th ris stai tr fl-a'i hi y u i flui h ou h he e voir 4}, the valves 87 are opened in order toivent air frq th yst m l lI llQ L ,lh val ss 8 ers a o v a fq rs ta tia ivqlamett balance to the system after refilling. -Briefly, ,samp s sd b u arti r hevl hi .qnaiia a t and .srei i a abot th .Ya l e v8'7 s th ,tb syste 2.0 is .o aectq d ectl t I YQi .4 nhweh el is .1. iQYe sl w ah ad or re tivel shor diseas say for example three or four fetgtderiable the aigles 13 and 14 to align themselves or in other words to enable the pistons in :the system to .move the required amount to place the system in balance 'or equilibriur n. When this condition exists the bypass' shut-bft :valves'87 are"closed and the axles are in their proper lpos'itions'iwith respect to the vehicle. i

Under some conditions it maybe advantageous 'to lock the .axles 13 and '14 against 'turning movement and this "may :be accomplished by closing communication through the respective sides 30 and 31 of the'hydraulic system 20. As shown .in Figure 1 of the drawingsfavalve 8'8 is provided for respectively closing communication through the conduits 30 and 3-1 of .the hydraulic system. Briefly, the .valve' 88 comprises a casing 89 vhaving the oppositeends respectively connected in the fluid conduits 30 and 31. A pair of vvalve plungers 90 are slidably supported in the casingi89and are normally urged to their innermost positions shown in Figure-l bysuitable springs 91. When the plungers are tinltheirrinnerrnost positions communication is established throughi theconduits 30 and 3:1, and communication between the latter "conduits through the valve 88 is prevented by the two vplung'ers. When'lit is desired to close communication through the respective conduits 30 and 31, .the valve plungers 90 are moved outwardlyfagainst the action of .the springs "91in .positions wherein they respectively close the conduits :30

and 31. Outward movement of the plungers 90 .is accomplished by connecting the interior of the casing 189 between the valve plungers 90 to a source of fluidunder pressure indicated'by the numeral 92. It will b.understoodthatwhen theivalve plungers 9t arein their'toutermost positions displacement of hydraulic fluid iin'both sides of thesystem 20 ispreventeclsothat the axlesvaie locked against turning movement.

"It follows r from the foregoing i that t the vehicle disclosed herein'iembodies asuspension 'system Whichincludes :two :steering axles 11-3 and 14 respectively supportediforxturning movement about substantiallyvertically extending-axes 17 and 1-9. The substantially verticallyextendin'g .axes :17and 19 arespaced forwardlyof :the respective axles inamanner such thatvthe ground engagingwheelsasso- .ciatediwith the respective axles will track with the front steering wheels (not shown) under normal operating conditions. Inother words, theconstruction is .suchithat .whenithe vehicle is turned fromra straight course of, travel by manipulationrof the front .steeringwheels, the pivoted axles v13, -14 .Will turn in the appropriate directions .to

,enable; then/heels .on the pivotedfaxles to conforrn'to-vthe steering pattern established-by the;.direction ofv-foryvard m0ti0n ofathe 'frontend of the: vehicle. The steering axles 13 and 14 :are actually turned' 'by .the resultantzlateral thrust developed at the point of engagement of ltheitilies .orrthe ground engaging-wheels with thelground. {lflhe spacingof the axles as well asthe distances-ibetween-the respective axles Land the vertical turning axes are acvcurately determined so that an-accurate progressiveinterrelation existsbetween theisteering movement. of the axles.

As previously stated, .forces other than? thoseencount- .ered during normal steering are frequently applied to lone or both axles during operation of thevehicle andithese forces =aregsubstantially overcomeby the -hydraulic-displacement :systern- 20. rIn general, the above rfOIQES are in the form of side thrustsapplied to the ground engaging .wheels and may result fromnurnerous different roadeonditions. In'any-eyent, the effect of unequal forgesappliedtto the steering axles is eliminated or renderedne gligible by, the hydraulic stabilizer-2ll.

In additionto the so-called lateralforcesvor side thrusts,

other situations may present themselves which requirestabilization. For example, 1 the elevation .of Lone wheel on 7 point where they are negligible insofar as their effect on the action of the vehicle running gear is concerned.

What I claim as my invention is:

1. In a vehicle having spaced pairs of ground engaging steering wheels respectively supported for turning movement about spaced vertically extending axes, stabilizing means connecting the wheels of one pair with the wheels of another pair, said means comprising a closed hydraulic displacement system filled with a hydraulic fluid and having spaced cylinders, pistons respectively slidably supported in the cylinders and respectively connected to the pairs of steering wheels by means including rods extending out of the cylinders at one end of the latter, a fluid conductor connecting the cylinders at one side of the pistons, a second fluid conductor connecting the cylinders at the opposite side of the pistons, a reservoir containing a supply of hydraulic fluid, aspirating valves having receiving chambers respectively in open communication with the conductors, air transfer chambers in said valves respectively connecting the receiving chambers to the reservoir, and a valve member in each valve normally positioned to close communication between the chambers of each valve and to open communication between the transfer chamber of each valve and said reservoir, thereby to displace air in said transfer chambers into said reservoir by hydraulic fluid from the latter, each valve member being operable by displacement of the fluid in the associated conductor to open communication between the chambers of each valve and to close communication between the transfer chambers of each valve and said reservoir, thereby to displace air in said receiving chambers into said transfer chambers by hydraulic fluid from the latter.

2. The structure defined in claim 1 wherein the receiving chambers of the valves are respectively serially connected to said conductors and wherein a baflie is located in each receiving chamber in a position to direct fluid toward the associated air transfer chamber.

3. The structure defined in claim 1 wherein the valve members have enlargements intermediate their ends respectively slidably supported in the air transfer chambers and coasting with the sides of the transfer chambers to provide a fluid bypass around the enlargements.

4. In a vehicle having spaced pairs of ground engaging steering wheels respectively supported for turning movement about spaced vertically extending axes, stabilizing means connecting the wheels of one pair with the wheels of another pair, said means comprising a closed hydraulic displacement system filled with a relatively non-compressible fluid and having spaced cylinders, pistons respectively slidably supported in the cylinders and respectively connected to the pairs of steering wheels by means including rods extending out of the cylinders at one end of the latter, a fluid conductor connecting the cylinders at .one side of the pistons, a second fluid conductor connecting the cylinders at the opposite side of the pistons, a reservoir containing a supply of relatively non-compressible fluid, aspirating valves comprising receiving chambers respectively in open communication with the conductors, air transfer chambers respectively positioned in said valves directly above the receiving chambers and communicating with the latter and with the reservoir, vertically extending free floating valve plungers in said valves having enlargements intermediate the ends thereof respectively slidably engaging the inner walls of the transfer chambers and having provision for fluid to bypass the enlargements, each valve plunger normally positioned to close communication between the chambers of each valve and to open communication between the transfer chamber of each valve and said reservoir, thereby to displace air in said transfer chambers into said reservoir by hydraulic fluid from said reservoir,

and each valve plunger being operable by displacement of fluid in the associated conductor to open communication between the chambers of each valve and to close communication between the transfer chambers and said reservoir, thereby to displace air in said receiving chambers into said transfer chambers by hydraulic fluid from the latter.

5. The structure defined in claim 4 wherein the lower ends of the valve plungers are exposed to the fluid passing through the respective receiving chambers of said valves and wherein said receiving chambers have baflles positioned to direct fluid upwardly toward the respective valve plungers.

6. Stabilizing means for spaced pairs of vehicle steering ground engaging wheels, comprising a closed hydraulic displacement system filled with a hydraulic fluid and having spaced cylinders, pistons respectively slidably supported in the cylinders and having operating rods respectively extending out of the cylinders at one end of the latter, a fluid conduit connecting the cylinders at one side of the pistons, a second fluid conduit connecting the cylinders at the opposite side of the pistons, a pair of aspirating valves having receiving chambers respectively in open communication with said conduits, air transfer chambers respectively positioned in said valves above the receiving chambers in communication with the latter, a hydraulic fluid reservoir communicating with the transfer chambers, a valve plunger in each valve normally positioned to close communication between the chambers of each valve and to open communication between the transfer chamber of each valve and said reservoir, thereby to displace air in said transfer chambers into said reservoir by hydraulic fluid from the latter, each valve plunger being operable by displacement of fluid in the associated conduit to open communication between the chambers of each valve and to close communication between the transfer chamber of each valve and said reservoir, thereby to displace air in said receiving chambers into said transfer chambers by hydraulic fluid from the latter.

7. Stabilizing means for spaced pairs of vehicle steering ground engaging wheels, comprising a closed hydraulic displacement system filled with a hydraulic fluid and having spaced cylinders, pistons respectively slidably supported in the cylinders and having operating rods respectively extending out of the cylinders at one end of the latter, a fluid conduit connecting the cylinders at one side of the pistons, a second fluid conduit connecting the cylinders at the opposite side of the pistons, a pair of aspirating valves having receiving chambers respectively serially connected in said conduits, air transfer chambers respectively positioned in said valves above the receiving chambers and connected to the receiving chambers through vertical passages, valve plungers respectively supported in the transfer chambers for vertical sliding movement and normally positioned with the lower ends thereof projecting into the passages for closing communication between the chambers of each valve, a hydraulic fluid reservoir connected to the transfer chambers at the top of the latter through second vertically extending passages aligned with the first passages for respectively receiving the upper ends of the valve plungers upon upward displacement of the latter to open communication between the chambers of each valve and to close communication between the transfer chambers and said reservoir, thereby to displace air in said receiving chambers into said transfer chambers by hydraulic fluid in the latter, said valve plungers in their normal position allowing for the displacement of air in said transfer chambers into said reservoir by hydraulic fluid from the latter.

8. The stabilizing means defined in claim 7 comprising baflles respectively projecting upwardly from the receiving chambers in positions to direct fluid upwardly against the valve plungers.

9. The stabilizing means defined in claim 7 having fluid connections between the respective receiving chambers and reservoir bypassing said valve plungers, and valves respectively located in said fluid bypass connections.

10. The stabilizing means defined in claim 7 wherein the length of the valve plungers is such that opposite ends thereof respectively project into the vertically aligned passages in intermediate positions of said plungers to prevent the flow of hydraulic fluid past the plungers.

11. The stabilizing means defined in claim 10 having fluid tight seals in each of said passages for engagement with the adjacent ends of the valve plungers.

12. In a vehicle having spaced pairs of ground engaging steering wheels respectively supported for turning movement about spaced vertically extending axes, stabilizing means connecting the wheels of one pair with the wheels of another pair, said means including a closed hydraulic displacement system filled with a hydraulic fluid and having cylinders, pistons respectively slidably supported in said cylinders, a fluid conductor connecting said cylinders at one side of said pistons, a second fluid conductor connecting said cylinders at the opposite side of said pistons, a reservoir containing a supply of hydraulic fluid, and aspirating valves respectively connecting said fluid conductors to said reservoir, each valve having means operable by the displacement of hydraulic fluid in the associated conductor for removing and transferring to said reservoir air accumulated in said conductor and replacing the same with hydraulic fluid from said reservoir.

13. In a vehicle having spaced pairs of ground engaging steering wheels respectively supported for turning movement about spaced vertically extending axes, stabilizing means connecting the wheels of 7 one pair with the wheels of another pair, said means including a closed hydraulic displacement system filled with a hydraulic fluid and having cylinders, pistons respectively slidably supported in said cylinders, a fluid conductor connecting said cylinders at one side of said pistons, a second fluid conductor connecting said cylinders at the opposite side of said pistons, a reservoir containing a supply of hydraulic fluid, and aspirating valves respectively connecting said fluid conductors to said reservoir, each valve having a passage communicating with the associated conductor and with said reservoir, means in said valve normally closing communication between the passage in each valve and the associated conductor, said last-named means being operable by the displacement of fluid in the associated conductor for removing and transferring to said reservoir air accumulated in said conductor and replacing the same with hydraulic fluid from said reservoir.

14. In a vehicle having spaced pairs of ground engaging steering wheels respectively supported for turning movement about spaced vertically extending axes, stabilizing means connecting the Wheels of one pair with the wheels of another pair, said means including a closed hydraulic displacement system filled with a hydraulic fluid and having cylinders, pistons respectively slidably supported in said cylinders, a fluid conductor connecting said cylinders at one side of said pistons, a second fluid conductor connecting said cylinders at the opposite side of said pistons, a reservoir containing a supply of hydraulic fluid, aspirating valves having air transfer chambers respectively connecting said conductors to said reservoir, means in each valve normally positioned to close communication between the chamber in each valve and the associated conductor and to open communication between the chamber of each valve and said reservoir, thereby to displace air in said chambers into said reservoir by hydraulic fluid from the latter, the means in each valve being operable by displacement of fluid in the associated conductor to open communication between the chamber of each valve and the associated conductor and to close communication between the chamber of each valve and said reservoir, thereby to displace air in said conductors into the associated chambers by hydraulic fluid from said reservoir.

References Cited in the file of this patent UNITED STATES PATENTS 1,700,394 Young Jan. 29, 1929 1,873,396 Hallenbeck Aug. 23, 1932 2,167,943 Fox Aug. 1, 1943 2,432,018 Keehn Dec. 2, 1947 2,632,462 Selwyn Mar. 24, 1953 FOREIGN PATENTS 61,649 Netherlands Aug. 17, 1948 

